1. Field of the Invention
The present invention relates to an improvement in a knapsack type working machine for doing work with a prime mover carried on an operator's back, e.g., a knapsack type bush cutter for cutting down bush or weeds.
2. Description of the Related Art
Working machines conventionally put into practical uses include a portable bush cutter which has a prime mover to be carried on an operator's back and an operational rod with a cutter provided at a distal end thereof and driven by the prime mover to thereby enable bush cutting.
Such knapsack type working machines having a prime mover to be carried on an operator's back are disclosed, for example, in Japanese Patent Publication No. SHO 60-50407 entitled "KNAPSACK TYPE BUSH CUTTER", Japanese Utility Model Publication No. HEI 5-45226 entitled "KNAPSACK TYPE WORKING MACHINE" and Japanese Utility Model Publication No. SHO 60-13849 entitled "KNAPSACK TYPE COLLECTION WORKING MACHINE".
The knapsack type bush cutter disclosed in Japanese Patent Publication No. SHO 60-50407 includes a prime mover carried on a single frame, a back plate provided on a front surface of the frame, and right and left shoulder straps provided on the frame. With the straps passed over the shoulders of an operator, the frame with the prime mover supported thereon can be carried on the operator's back via the back plate during bush cutting operations.
The knapsack type working machine disclosed in Japanese Utility Model Publication No. HEI 5-45226 is featured in a detachment device for allowing detachment, when required, of a frame carrying a prime mover from an operator's back through detachment of shoulder straps from the frame.
The collection work machine disclosed in Japanese Utility Model Publication No. SHO 60-13849 has a prime mover carried on a single frame with shoulder straps so that the frame and hence the prime mover can be carried on an operator's back while collecting fallen leaves or sprinkling a chemical liquid with a jet of air generated by the prime mover.
As described above, each conventional machine is comprised of the prime mover carried on the single frame, and the shoulder straps provided on the frame so that the frame with the prime mover can be carried on the operator's back during operations thereof. In other words, the prime mover and the frame are fixedly connected together to form a single body.
In the described machines, since the prime mover and the frame having the back plate and the shoulder straps are fixedly connected together, the frame and the back plate present an obstruction to the maintenance of the prime mover, thereby making such maintenance inefficient.
For storing the machines when the latter are not in use, care must also be taken of the frame and the back plate, thereby rendering the storage tedious and time consuming. Upon storage, since the prime mover, frame, back plate and shoulder straps are all connected together, there is a fear that an oil and/or grease oozed out from the prime mover clings to the straps and back plate, thereby dirtying machine portions other than the prime mover. When the machines with those dirtied portions are stored in a small storehouse, those dirtied portions may in turn dirty the surroundings, thereby limiting the places for storage of the machines.
Further, since they include the prime mover, frame, back plate and straps connected together to form a single body, the machines are elongated and become large in overall size, thereby requiring a large storage space.
In the knapsack type working machine disclosed in Japanese Utility Model Publication No. 5-45226, the shoulder straps are designed such that they can be detached from the frame easily. However, the frame including the prime mover is fixedly Joined with the back plate and shoulder straps. Thus, the machine has the same problems as discussed above.
Consequently, arrangements are demanded in which the prime mover can be separably carried on the support frame and hence from the machine as an entirety, thereby increasing efficiency in the maintenance thereof.
The working machine with the prime mover being separable from the support frame or the machine is advantageous in that it can be stored in a small storehouse easily. With the prime mover being separable from the back plate or a back frame including the back plate and shoulder straps, it becomes possible to prevent the machine portions other than the prime mover from being dirtied by the prime mover upon storage of the machine. In addition, by virtue of the arrangements, cleaning of the prime mover, back plate and shoulder straps can be performed easily.
There is also a demand for the provision of an arrangement which allows the prime mover to be separated from the back frame instantly as if by a single touch and which is simple in construction.